1. Field of the Invention
The present invention relates to a method of fixing connection parts of rubber offshore structures such as marine fender, oil boom, marine hose, sleeve hose and the like.
2. Description of the Prior Art
In general, bolt and nut means are widely used as a method of fixing a marine fender constructed with a shock receiving portion, supporting portions and securing portions to a supporting surface of a quay wall or the like. In recent years, however, vessels are considerably large-sized and hence the inertia force of the vessel becomes very high, so that the shock-receiving portion and the securing portions of the marine fender are obliged to receive a strong berthing impact force during berthing and mooring of such large-sized vessel. Furthermore, it is actually very difficult to avoid the berthing of the vessel inclined at a certain angle with respect to the marine fender during the steering. In the latter case, excessive stress load is applied to a local area of the marine fender contacting with the vessel, so that the marine fender itself is deformed and damaged. And also, a large force is applied to the securing portion of the marine fender, so that the bonding of bolts to nuts becomes loose and consequently the fixed state of the marine fender to the quay wall becomes unstable. Moreover, when the marine fender is excessively compressed by the berthing impact force, an outer wall of the supporting portion of the marine fender may be damaged by contacting with the bolts and nuts in the securing portion.
In use, the marine fender is influenced by sea water, so that the bolts and nuts are apt to be corroded. This corrosion extends to a metal plate member embedded in the securing portion adjoining to the bolts and nuts and as a result, the adhesion of the metal plate member to rubber of the securing portion is decreased, so that a fatal damage is given to the marine fender.
In order to prevent the loosening of the bolts and nuts, there has hitherto been used a method of fixing a head portion of bolt to a metal rod attached to quay wall by welding. However, this welding method requires a great amount of skill in the welding operation and also there is a risk in the welding operation near oil-existing places because sparks fly during the welding. Furthermore, protrusions are formed on the welded part, so that this welding method is unfavorable if it is intended to prevent damaging on the outer wall of the supporting portion in the marine fender. In order to prevent the corrosion of bolts and nuts, there is attempted the use of stainless steel as a material for bolts and nuts. However, the stainless steel is expensive in cost and also there is no effectivity for preventing the corrosion of the metal plate member embedded in the securing portion. In order to prevent the damaging on the outer wall of the supporting portion of the marine fender, there is known a method of covering each head portion of the bolts and nuts with a rubber cap wherein the rubber cap is adhered to the bolt and nut with a usual adhesive. However, this adhesive does not serve to fill up a gap enough, so that it is necessary to widen the adhesive surface area by applying a pressure in order to provide a satisfactory adhesion. Furthermore, it is very difficult to hold the rubber cap covering the bolt and nut at the contact bonding state and as a result, the sealing by the rubber cap is incomplete. Therefore, the use of the rubber cap is not effective for preventing the loosening and corrosion of the bolt and nut.
In general, the loosening and corrosion of the metal fixing member as described above come into question to rubber offshore structures such as marine hose, sleeve hose, oil boom and the like besides the marine fender.